In recent years, in the field of toners for electrophotography, with the progress of electrophotographic systems, it has been demanded to develop toners adaptable for high image quality and high copying or printing speed. From the viewpoint of the high image quality, the toners have been required to have a small particle size. Thus, there have been disclosed processes for producing a so-called chemically prepared toner by a chemical method such as a suspension polymerization method, an emulsion polymerization method and a dissolution suspension method in place of the conventional melt-kneading method. Further, from the viewpoint of the high copying or printing speed, there has been reported a chemically prepared toner to which a releasing agent is internally added in order to improve low-temperature fusing property thereof.
For example, Patent Literature 1 discloses a toner including core particles produced by aggregating at least resin particles, colorant particles and wax particles, in which a dispersant used in a dispersion of the wax particles contains a polypropylene glycol ethyleneoxide adduct. Patent Literature 1 also describes that the problem that the wax particles or the colorant particles are not aggregated with the other components of the core particles in an aqueous system and therefore remain unincorporated into the core particles can be solved, so that it is possible to produce toner particles having a narrow particle size distribution and a small particle size.
Patent Literature 2 discloses a process for producing a toner including the steps of mixing resin particles containing a polyester as a main component, releasing agent particles containing a wax and a polyester resin having a specific softening point at a specific weight ratio, and an aggregating agent in an aqueous medium to obtain aggregated particles (1); mixing the aggregated particles (1) with polyester-containing resin particles serving as a shell to obtain aggregated particles (2); and coalescing particles constituting the aggregated particles (2) to obtain core-shell particles. In Patent Literature 2, it is described that the toner obtained by the production process is excellent low-temperature fusing property and heat-resistant storage stability.
Patent Literature 1: JP 2010-169702A
Patent Literature 2: JP 2012-128024A